1. Field of the Invention
The present invention is related with adaptive video recording and reproducing systems. Video signals, which are outputted from two or more video sources, such as a video camera etc., are inputted to the system. The system switches the video signals, and records it to a recording medium of random access type etc. by a field unit or a frame unit. The system reproduces selectively the image of the video source.
2. Description of the Related Art
There is a security system, in which two or more video cameras are installed for the purpose of superintendence, such as a crime prevention, and each video image is monitored. In such a system, an apparatus for simultaneously recording two or more video images and reproducing them later for the verification etc. in the future, is required. As a system to which the output signals of two or more video sources, such as a video camera, are inputted, and records them, a construction having a plurality of recording devices whose number is equal to that of the video sources, may be considered. However, in this case, the apparatus constitution becomes large-scale, and the cost-up cannot be avoided.
In order to overcome such a problem, there is a transmitting, recording and reproducing method of two or more movable images by use of a time division technique, which is disclosed in the Japanese Patent Application Laying Open No. (Hei) 3-13190. Or, there is a recording and reproducing method disclosed in the Japanese Patent Application Laying Open No. (Hei) 3-190387. According to the method in the Japanese Patent Application Laying Open No. (Hei) 3-13190, the process is performed such that two or more movable image data are switched to a field or frame unit, and are transmitted as a single synthetic image data signal. The field or frame signal is separated from the received synthetic image data signal. By a counter, only the desired image data signal is written into a field or frame memory, so that the target movable image data is reproduced. On the other hand, according to the method disclosed in the Japanese Patent Application Laying Open No. (Hei) 3-190387, the process is performed such that two video signals are switched for every field, and are recorded onto a magnetic tape. At the time of reproduction, only one image is reproduced independently, by the cycle of field-switching at the time of recording.
However, there are the following problems in these methods mentioned above. Namely., it switches two or more video signals for every field, and generates a single synthetic video signal. It records the generated signal, sequentially and continuously on the magnetic tape. Alternatively, it only transmits the signal and selectively displays it. Therefore, by selecting the desired video image by a fixed timing, the reproduction of the movable image can be performed relatively easily. However, it is hard to treat the video image by a field unit or a frame unit. It is not easy to carry out various displays etc. in the recording and reproducing operations, such as a security system and a central managing system.
Moreover, in case of recording to the magnetic tape, it is not easy to control to access the image of the desired frame independently from the recorded physical position, so that the long access time is also needed. Further, in case of such a usage that, for example, the number of video sources, such as the number of the installed video cameras, are changed, the greatest recording area must be always set and prepared, so that, when the number of input is few, the futility arises in the recording area.
Secondly, by the security system or the central managing system, such a case often arises that there is no change in the object to monitor. For this reason, the still image without any change is recorded continuously, so that the futility arises in the recording area, too.